The present invention relates to a thermosensitive recording adhesive label which is capable of performing thermosensitive recording thereon and more particularly to a thermosensitive recording adhesive label capable of retaining recorded images for a long period of time, without being affected by any organic resinous films which happen to come into contact with the label.
Adhesive labels are used for various purposes. For instance, they are attached to commercial products for indicating their names, contents, prices, qualities, etc., or to postal matters for indicating their destinations. Conventionally, those are written by stamping ink or by typing. The stamping method has a shortcoming in that it requires replenishment of ink from time to time, while the typing method has a shortcoming in that used typewriter ribbons have to be replaced by new ribbons from time to time.
Under such circumstances, application of thermosensitive recording to such adhesive labels has been desired, since that application could eliminate the above-mentioned shortcomings of the conventional adhesive labels. However, that, too, heretofore had a significant shortcoming as will now be explained. At present, the most practical thermosensitive recording materials are of a type employing a thermosensitive coloring material comprising a colorless or light-colored leuco dye and an acidic material for coloring the leuco dye when heat is applied thereto, since images produced by the thermosensitive coloring material are clear and do not deteriorate with time, and those thermosensitive recording materials themselves can be stored for a long period of time without fog.
When adhesive labels employing the above-mentioned thermosensitive recording material are used for commercial products, it may occur that the label is covered with a polyvinylchloride resin film or a polypropylene film to protect the image formed on the label, or the label is applied to products covered with the above-mentioned films. In the circumstances, however, in the case of the conventional thermosensitive recording adhesive label, the images formed on the label lose their color and become illegible in about half a day while in contact with the above-mentioned polyvinylchloride resin film or polypropylene film.
The same is true of the thermosensitive recording adhesive labels for use with postal matters. Due to this shortcoming, the thermosensitive recording materials comprising leuco dyes and acidic materials have not been successfully applied to adhesive labels attached to commercial products or postal matters.